| 摘要 |
A data communication apparatus which causes the eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability is provided. In a modulator section 112 a, a branching section 114 branches a lightwave 20 outputted from a light source 113 , and outputs respective branched lights to a first light path 117 and a second light path 118 respectively having different light path lengths. A light modulator section 116 modulates, based on a multi-level signal 13 , a lightwave propagating at least one light path of the first light path 117 and the second light path 118 . An interference section 119 causes the lightwaves outputted from the first light path 117 and the second light path 118 to interfere with each other, and outputs such interfered lightwave as a modulated signal 14.
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